Cleanup: Remove some NULL checks in fpdfsdk.

fpdfsdk/src/formfiller/FFL_IFormFiller.cpp

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "../../include/formfiller/FFL_FormFiller.h"
 #include "../../include/formfiller/FFL_IFormFiller.h"
 #include "../../include/formfiller/FFL_CheckBox.h"
 #include "../../include/formfiller/FFL_ComboBox.h"
@@ skipping 547 matching lines @@
   }
 
   if (!pFormFiller)
     return nullptr;
 
   m_Maps[pAnnot] = pFormFiller;
   return pFormFiller;
 }
 
 void CFFL_IFormFiller::RemoveFormFiller(CPDFSDK_Annot* pAnnot) {
-  if (pAnnot != NULL) {
+  if (pAnnot) {
     UnRegisterFormFiller(pAnnot);
   }
 }
 
 void CFFL_IFormFiller::UnRegisterFormFiller(CPDFSDK_Annot* pAnnot) {
   auto it = m_Maps.find(pAnnot);
   if (it == m_Maps.end())
     return;
 
   delete it->second;
@@ skipping 293 matching lines @@
           bExit = TRUE;
           m_bNotifying = FALSE;
           return;
         }
       }
 
       m_bNotifying = FALSE;
     }
   }
 }